Optical disk apparatus and data randomizing method using for optical disk apparatus

ABSTRACT

In the optical disk apparatus, an arbitrary seed data for randomizing is added to an original data to be recorded on a disk. One-bit randomizing data is determined by operation using one-bit original data or seed data, and plural-bit past randomized data. At the time of descrambling, descrambling is performed without seed data.

FIELD OF THE INVENTION

This invention relates to an optical disk apparatus such as DVD or thelike and particularly to the data scramble method in recording data on amedium in the optical disk apparatus.

BACKGROUND OF THE INVENTION

Generally, in a rewritable optical disk such as DVD-RAM or the like, arecording mark is generated on a track of a disk by power of light tothereby write data. Further, data is read out by utilizing a differencein reflectance of light between the recording mark and a portion outsidethe mark. In the DVD-RAM, a groove is formed on a disk, and data iswritten on both the groove and a non-groove portion (land) to attainhigh density recording.

The control for accurately positioning a head on the track is calledtracking. In the DVD-RAM, micro-vibrations of a land and a groove, whichare called wobble, are caused, and tracking is performed by utilizingthem. When the same data is written in the adjacent tracks, however, theproblem encountered is that a tracking signal becomes feeble andtracking tends to slip. In the DVD for processing an image and sounddata, frequently the same data such as a silent portions is written in alarge amount. To solve this problem, various measures have been taken sothat even if a large amount of the same data is written, the writtendata in the adjacent tracks do not become the same. According to amethod disclosed in Japanese Patent Laid-Open No. Hei 6(94)-274885, forexample, the beginning of a sector begins at a mark called pit or anon-mark portion called land alternately track by track. Further,according to a method described in ECMA-272 “120 mm Rewritable Disk(DVD-RAM)”, in the DVD-RAM, ID information of each frame is taken as aseed to generate a M-sequence (random sequence), and the M-sequence isadded to the user data to be written in a disk. Such data randomizing isgenerally called scramble.

On the other hand, in field of optical communication, a method calledguided scramble has been adopted for the purpose of creating arun-length limited code having a flat frequency characteristic suitablefor optical communication. According to this method, data having anenough large space is added to the beginning of the data to create arun-length limited code, thereby producing many kinds of data, and amongthe data obtained by randomizing the thus produced data, one data near arequired characteristic is selected. This method is described in detailin “Codes for Mass Data Storage Systems” K. A. S. Immink, ShannonFoundation Publishers, 1999. Further, as a paper, this method isdescribed in “Polynomials for Guided Scrambling Line Code”, IEEE JOURNALON SELECTED AREAS IN COMMUNICATIONS, Vol. 13, NO. 3, APRIL. 1995.

SUMMARY OF THE INVENTION

The rewritable optical disk, however, has the problem that when the samedata is written many times in the physically same place (sector) on anoptical disk medium, the medium changes in quality, and when new data iswritten, the remained former data tends to be viewed as a noise.

According to the invention, to solve the above problem, data isscrambled by making use of an arbitrary seed. Preferably, arbitrary seeddata for performing randomizing is added to the original data to berecorded on a disk. One bit randomizing data is determined by operationusing one bit original data or seed data and multiple-bits pastrandomized data.

Further, to solve the above problem, the invention adopts a descramblingmethod not requiring seed data. To be concrete, at the time ofreproducing data, used is a data randomizing release method which ischaracterized in that one bit de-randomizing data is determined byoperation using multiple-bits randomized data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a scrambling circuit according to theinvention;

FIG. 2 is a block diagram showing a descrambling circuit according tothe invention;

FIG. 3 is a schematic block diagram of an optical disk apparatusaccording to a first embodiment of the invention;

FIG. 4 is a detailed block diagram of a scrambling circuit in the firstembodiment of the invention;

FIG. 5 is a detailed circuit diagram of a M-sequence generator in thefirst embodiment of the invention;

FIG. 6 is a detailed circuit diagram of a secondary scrambling circuitin the first embodiment of the invention;

FIG. 7 is a detailed block diagram of the descrambling circuit in thefirst embodiment of the invention;

FIG. 8 is a detailed circuit diagram of a secondary descrambling circuitin the first embodiment of the invention;

FIG. 9 is a conceptual drawing of the first embodiment;

FIG. 10 is a diagram showing a data sector format;

FIG. 11 is a diagram showing a physical sector format in the secondembodiment of the invention;

FIG. 12 is a diagram showing a recording format in the second embodimentof the invention;

FIG. 13 is a conceptual drawing showing a PO interleave;

FIG. 14 is a system block diagram in the second embodiment of theinvention;

FIG. 15 is a processing flowchart of recording in the second embodimentof the invention;

FIG. 16 is a processing flowchart of reproduction in the secondembodiment of the invention;

FIG. 17 is a schematic block diagram of an optical disk apparatusaccording to a third embodiment of the invention;

FIG. 18 is a block diagram of an optical disk apparatus according to thethird embodiment of the invention;

FIG. 19 is a processing flowchart of recording in the third embodimentof the invention;

FIG. 20 is a processing flowchart of reproduction in the thirdembodiment of the invention;

FIG. 21 is a diagram showing a physical format in a fourth embodiment ofthe invention;

FIG. 22 is a diagram showing grouping of seeds in the fourth embodimentof the invention;

FIG. 23 is a diagram showing a fixed SYNC pattern in the fourthembodiment of the invention;

FIG. 24 is a diagram showing a recording format in the fourth embodimentof the invention;

FIG. 25 is a block diagram of an optical disk apparatus according to thefourth embodiment of the invention;

FIG. 26 is a system block diagram in the fifth embodiment of theinvention;

FIG. 27 is a block diagram showing a scramble circuit according to thefifth embodiment of the invention;

FIG. 28 is a diagram showing a another data sector format in the secondembodiment of the invention;

FIG. 29 is a another system block diagram in the second embodiment ofthe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 3 is a block diagram showing the configuration of an optical diskapparatus according to the first embodiment of the invention. Theembodiments described in the following will not set limits to theinvention, but the optical disk apparatus may be recording andreproducing apparatus such as a deferred image and voice recording andreproducing apparatus connected to a television set, a portable videocamera or a portable voice reproducing apparatus in addition to astorage device used in the computer system as in the present embodiment.

In FIG. 3, a host interface (host I/F) 311 controls the data transferbetween the optical disk apparatus and a host computer such as apersonal computer not shown. A scrambling circuit 309 randomizes data.An error correcting encoding circuit 307 adds an error correcting codeto the randomized data. A run length limited encoding circuit 305modulates the data to which an error correcting code is added accordinga predetermined rule to be converted to data which can be recorded on anoptical disk 301 as a recording medium. A recording and reproducingamplifier 303 receives coded data from the run length limited encodingcircuit 305, and converts the same to a voltage waveform suitable for arecording and reproducing head 302. The recording and reproducing head302 converts the received voltage waveform to optical laser, and writesa mark on the optical disk 301 by optical power.

At the time of reading the data, the recording and reproducing head 302applies a laser light to the optical disk 301 to read the data byreflected light by utilizing a difference in reflection intensity oflight between a mark and a non-mark part, and converts the readinformation to an electric signal. The converted electric signal ismoderately amplified by the recording and reproducing amplifier 303, andthen output to a data reproducing circuit 304. The data reproducingcircuit 304 converts a read analog signal to a digital information rowof 0 and 1.

The data row is demodulated in reverse to the run length limitedencoding circuit 305 by a run length limited code decoding circuit 306.In an error correcting circuit 308, on the basis of the error correctingcode added by the error correcting encoding circuit 307, the errorposition and the error value are obtained to correct the error. The datasubjected to error correction is restored to the original data by adescrambling circuit 310. In the optical disk apparatus, the data isrecorded and reproduced according to the above procedure.

FIG. 4 is a block diagram of the scrambling circuit 309.

User data sent from the host I/F 311, to which a fixed random sequencemade by a M-sequence generator 401 has been added in an EOR circuit 402,is input to a guided scrambler 403.

FIG. 5 is a circuit diagram of the M-sequence generator 401. Thereference numerals 502 to 515 are registers for storing data in units ofone bit, which conduct shift operation in synchronization with the userdata. The reference numeral 501 is an exclusive-OR circuit. In theinitial state, only the register 515 is set to one, and the registers502 to 514 are set to zero. In the present embodiment, supposed is anM-sequence generator using a polynominal of the fifteenth degree shownin the expression 1. In the following, polynominals used in the presentembodiment are all polynominals on GF (2), and “+” indicates anexclusive-OR.x ¹⁵ +x ⁴+1  (1)

A sequence generated by the M-sequence generator 401 is a pseudo-randomsequence with a period of 2¹⁵−1=32767. In the present embodiment, theM-sequence generator 401 is not always needed, but only the guidedscrambler 403 will be sufficient. To improve random performance,however, in the present embodiment, the M-sequence 401 is jointly used.

The guided scrambler 403, as shown in FIG. 9, adds 8-bit data to thebeginning of the data. The added data is an arbitrary 8-bit data. Forexample, it may be the data generated on the basis of time when data iswritten or the value incremented one by one at every writing by an 8-bitincrement counter. This 8-bit added to the beginning of the data becomesan initial value (seed) for randomizing. As the 8-bit data is added inthe embodiment, randomizing can be performed in 2⁸=256 ways, from“00000000” to “11111111”. That is, in the case of recording the sameuser data in the physically same place, the probability that theactually written data becomes the same is 1/256. The same may be said ofthe case of writing the same user data in the adjacent track.

Randomizing is thus performed to avoid deterioration of the optical disk301, so that a tracking error can be reduced. The added data should notbe always 8-bit, but further more or less may be good. The added-bit(initial value) should not be attached to the beginning of the userdata, but be put in an arbitrary portion of the user data. The user dataon and after the portion where the added-bit is added is generated as asequence varied with every initial value. In the embodiment, added datais placed at the beginning which enables randomizing most efficiently.However, in the case where there is information such as ID informationto be read before descrambling, it is better to insert the added-bitafter the ID information or the like.

FIG. 6 is a circuit diagram of a secondary scrambling circuit 405. Thereference numerals 601 to 604 are exclusive-OR circuits. The referencenumerals 605 to 612 are registers for storing data in units of one bit.The registers 605 to 612 are set to zero in the initial state. Thesecondary scrambling circuit 405 conducts shift operation insynchronization with the input data.

By this circuit, scrambling is performed according to the expression 2.c _(i) =b _(i) +c _(i−4) +c _(i−5) +c _(i−6) +c _(i−8)  (2)

wherein bi is i-th bit data before entering the secondary scramblingcircuit 405, and ci−j is data j bits ahead of the i-th bit data outputfrom the secondary scrambling circuit. It is known from the expressionthat ci is created from one bit data before scrambling and multiple-bitpast data after scrambling.

The scrambled data is sent to the error correcting encoding circuit 307.

FIG. 7 is a block diagram of the descrambling circuit 310. FIG. 8 is acircuit diagram of the secondary descrambling circuit 704 shown in FIG.7. The reference numerals 801 to 808 are registers for storing data inunits of one bit. The reference numerals 809 to 812 are exclusive-ORcircuits. The secondary descrambling circuit 704 also conducts shiftoperation in synchronization with input data similarly to the secondaryscrambling circuit 405.

The operation of the descrambling circuit 310 will now be described.

The data subjected to error correction by the error correcting circuit308 is input to the secondary descrambling circuit 704 of the guideddescrambling circuit 703. By the secondary descrambling circuit 704,descrambling shown in the expression 3 is performed.b _(i) =c _(i) +c _(i−4) +c _(i−5) +c _(i−6) +c _(i−8)  (3)

wherein bi is i-th bit user data descrambled, and ci-j is data j-bitahead of i-th bit data input from the error correcting circuit 308. Inthe case where the descrambling circuit performs descrambling, even ifthe initial value of scrambling is not known, descrambling is enabled.In the case where an error which can not be corrected by the errorcorrecting circuit 308 occurs, in the descrambled user data, the erroris extended for 8 bits. However, error propagation is caused only for 8bits, and more propagation will not be caused.

In the descrambled user data, as shown in FIG. 9, an 8-bit added by arandom data adding circuit 404 is deleted by a-random data deletingcircuit 705.

An M-sequence generator 701 is the same as the M-sequence generator 401,and shown in FIG. 5. The user data is descrambled by adding the same inthe exclusive-OR circuit 402.

Though the scrambling circuit is formed by using shift registers for bitshifting in the embodiment, it may be effected by using an equivalentcircuit operated in byte units.

In the embodiment, an 8-bit source polynominalx ⁸ +x ⁴ +x ³ +x ²+1  (4)

is used to perform guided scrambling, but any polynominal will be usedhere if it is a source polynominal. For the general form of apolynominal

$\begin{matrix}{\sum\limits_{i = 0}^{n}{a_{i}x^{i}}} & (5)\end{matrix}$

, the scrambling circuit can be implemented in FIG. 1, and thedescrambling circuit can be implemented in FIG. 2. In the expression,a_(i) is 1 or 0, and in the case of 1, a signal line is connected, andin the case of 0, a signal line is not connected.

Though the scrambling circuit 309 and the descrambling circuit 310 arerespectively provided between a set of the error correction encodingcircuit 307 and decoding circuit 308 and the host I/F 311 in theembodiment, they may be provided between a set of the run length limitedencoding circuit 305 and decoding circuit 306 and a set of the errorcorrection encoding circuit 307 and decoding circuit 308. Further,though the M-sequence generators 401, 701 are disposed on the host I/F311 side from the guided scrambling circuit 403 and the descramblingcircuit 703, respectively, in the embodiment, the M-sequence generators401, 701 may be arranged on the optical disk 301 side from the guidedscrambling circuit 403 and the descrambling circuit 703, respectively.

FIG. 14 is a block diagram of a second embodiment of an optical diskapparatus to which the invention is applied. The present embodiment isthe mode for carrying out the invention in the case of applying theguided scrambler described in the first embodiment to a DVD apparatus.

The reference numeral 311 designates an interface for conducting thedata input and output control to a host device. The reference numeral1406 is a microcomputer for supervising the system. The referencenumeral 1401 is an ID adding device for adding additional informationrequired for recording ID or the like to the user data given by theinterface 311. The reference numerals 1402 a and 1402 b are memories(RAM) for temporarily storing data. The reference numeral 309 is ascrambler for randomizing data. The scrambler 309 is the same asdescribed in the first embodiment and includes a fixed seed M-sequencegenerator and a guided scrambler. The reference numeral 307 is an errorcorrecting encoding circuit for adding an error correcting code to thescrambled user data. The reference numeral 305 is an encoder forconverting the user data to which an error correcting code is added to arun length limited code suitable to be recorded in the optical disk 301.The reference numeral 302 is a pickup for recording and reproducing datato and from the optical disk 301. The reference numeral 1403 is aspindle motor for rotating the disk. The reference numeral 1404 is aservo for conducting the control for an optical pickup 302 or the like.

The reference numeral 304 is a read channel for conducting waveformequalization processing and binarization for an analog signal read fromthe optical disk 301, and synchronous clock generation. The referencenumeral 306 is a decoder for decoding a read run length limited code.The reference numeral 308 is an error detection correcting circuit fordetecting an error according to an error correcting code added by theerror correction encoding circuit 307 and correcting the error. Thereference numeral 310 is a descrambling circuit described also in thefirst embodiment for releasing randomizing performed by the scrambler309 to restore to the original user data. The descrambling circuit 310includes a fixed seed M-sequence generator and a guided descrambler. Thereference numeral 1407 is an ID delete device for deleting additionalinformation required for recording ID or the like added by the ID adder1401 to be only the user data.

A write format for the user data will now be described according toFIGS. 10 to 13.

To 2048-byte user data, for example, input from the interface 311,11-byte data identification address information such as ID or the like(ID part 1001, IED part 1002, a reserve part 1003) and 4-byte errordetection code (EDC: Error Detection code) 1006 are added by the IDadding device 1401.

The data to which information such as ID or the like is added isscrambled by adding one-byte guided scrambling seed 1004. Only the maindata (user data) 1005 and the error detection code 1006 are to bescrambled, and the identification address information such as ID or thelike is not scrambled. Eleven bytes of ID or the like, one byte ofscrambling seed, 2048 bytes of user data, and four bytes of EDC areadded to amount to 2064 bytes. The 2064 bytes of data is formed by 172bytes ×12 lines. This is called “data sector”. Subsequently, as shown inFIG. 12, sixteen “data sectors” are collected to be taken as one ECCblock, and a cross read Solomon error correcting code is encoded. Thelongitudinal redundant byte is called PO, and the lateral redundant byteis called PI.

As shown in FIG. 13, sixteen lines of POs are allocated line by line tosixteen sectors to be rearranged to 172 bytes×(12+1) line. This iscalled PO interleaving, and the data of 172 bytes×(12+1) line is called“recording sector”. A “physical sector” shown in FIG. 11 is a sectorobtained by adding a synchronous signal (SYNC code) 1101 to thebeginning of every 91 bytes of the “recording sector” 1102, andperforming modulation by 8/16 conversion. EDC 1006 shown in FIG. 10 is acheck code attached to the data sector 2060 bytes before scrambling. Bythe EDC code 1006, it is checked whether wrong correction is made ornot.

In a user's write format, as shown in FIG. 28, a seed may be added tothe beginning. In this case, data identification address information 11bytes (1001, 1002, 1003) such as ID, ID of a reserve or the like anddetecting code (EDC: Error Detection Code) 4 bytes are scrambledsimilarly to the data. In the case of this format, deterioration of amedium of the ID part can be prevented. In the case of adopting theformat shown in FIG. 28, it is necessary to place a special descrambler1408 special for the ID part immediately after signal reproducingprocessing of PRML and read ID before decoding the ECC as shown in FIG.29.

The operation in the DVD apparatus shown in FIG. 14 will be described.

FIG. 15 is a flowchart showing the procedure at the time of recording.

The ID adding circuit 1401 adds ID and additional information to datainput from the interface 311 (Step 1501). The information to which ID orthe like is added is temporarily stored in the RAM 1402 a (Step 1502).The scrambling circuit 309 reads data from the RAM 1402 a (Step 1503)and conducts scrambling processing (Step 1504. The error correctionencoding circuit 307 adds an error correcting code to the scrambled data(Step 1505, and stores the same together with the scrambled data, POredundant byte and PI redundant byte in the RAM 1402 a (Step 1506. Thestored data is subjected to PO interleaving (Step 1507. The encodingcircuit 305 converts the data subjected to PO interleaving to a runlength limited code (Step 1508. The data converted to the run lengthlimited code is recorded on the optical disk 301 through a laser driver1405 by the optical pickup 302.

When normally the data for one ECC block is recorded on the optical disk301, the processing is ended. When a recording failure is caused in themidway by some reason, writing of the same data on the same place willdeteriorate a medium. In this case, a seed is changed, and re-scramblingis performed to try again. In the flowchart of FIG. 15, the processingof the step 1503 and its followings are again conducted.

FIG. 16 is a flowchart showing the procedure at the time of reproducing.

At the time of reproducing, the optical pickup 302 reads data from themedium, and the read channel 304 performs binarization and synchronousclock generation (Step 1601 . The decoding circuit 306 decodes a runlength limited code (Step 1602, and while PO deinterleaving reverse toPO interleaving is performed, the data is temporarily stored in the RAM1402 b (Step 1603. Error correction (Step 1604 and descrambling (Step1605 are conducted through the RAM 1402 b, and the descrambled data isagain stored in the RAM 1402 b (Step 1606. Further, in the step 1606,the data stored in the RAM 1402 is read (Step 1607, and by the EDC code1006, it is checked whether wrong correction is made or not. After that,additional information such as ID or the like and a seed are deletedfrom the data, which is output to the interface 311 (Step 1608).

According to the present embodiment, scrambling is released after theerror correction processing is ended similarly to the first embodiment,so that the error correction capability is not deteriorated by errorpropagation of guided scrambling. Furthermore, as the present embodimenthas configuration close to that of the current DVD apparatus, theapparatus can be easily developed.

Though a seed is added to every 2K byte of one sector user data in thefirst embodiment, guided scrambling may be performed with one seed inone ECC block to hold down a storage area of the seed. To be concrete,there are a method of consecutively processing one ECC block by oneguided scrambling process and a method of processing the respectivesectors of one ECC block with the same seed by the guided scramblingprocess. Further, since guided scrambling causes error propagation, itbeing taken into account that when error correction is disabled, data isrelieved even in a small amount, it is desirable that as shown in theembodiment, scrambling is performed along the byte list of an errorcorrecting code word in the case of conducting scrambling processingcloser to the user side than the error correction encoding processing.Thus, when a large burst error occurs to disable error correction,scrambling can be released to the extent that one byte error propagationis caused from the final bit of the burst error.

FIG. 18 is a block diagram showing a third embodiment of an optical diskapparatus to which the invention is applied. The present embodiment hasthe same configuration as that of the optical disk apparatus in thesecond embodiment, but the differences from the second embodiment arethe arrangement of the scrambling circuit 309 and the descramblingcircuit 310, and the procedure of error correction encoding 307 andscrambling processing 309.

FIG. 19 is a flowchart showing the procedure at the time of recording.

The ID adding circuit 1401 adds ID and additional information to datainput from the interface 311 (Step 1901. The data to which ID or thelike is added is temporarily stored in the RAM 1402 a (Step 1902. Theerror correction encoding circuit 307 reads data from the RAM 1402 a(Step 1903, calculates an error correcting code (Step 1904, and writesan error correcting code portion in the RAM 1402 a (Step 1905.

While data is read from the RAM 1402 a, PO interleaving is performed(Step 1906, and scrambling processing is conducted for the data readfrom the RAM 1402 a (Step 1907. After that, encoding circuit 305converts the scrambled data to a run length limited code (Step 1908. Thedata converted to the run length limited code is recorded on the opticaldisk 301 through the laser driver 405 under the control of the opticalpickup 302.

When normally the data for one ECC block is recorded on the optical disk301, it comes to end. In the case where a recording failure is caused inthe midway by some reason, writing of the same data in the same placewill deteriorate the medium. Therefore, the seed is changed to performre-scrambling, and the processing is again conducted. In the flowchartof FIG. 19, the processing of the step 1906 and its followings are againconducted.

In the case of redoing writing in the present embodiment, it is notnecessary to again calculate an error correcting code, so that load atthe time of rewriting can be lowered. Furthermore, as it is notnecessary to save the scrambled data in the RAM, the frequency of accessto the RAM is reduced so that high speed processing is attained.

FIG. 20 is a flowchart showing the procedure of reproducing.

The optical pickup 302 reads data from the recording medium, and theread channel 304 performs binarization and synchronous clock generation(Step 2001. The decoding circuit 306 decodes scrambled data from a runlength limited code (Step 2002. The descrambling circuit 310 conductsdescrambling processing (Step 2003. The descrambled data is subjected toPO deinterleaving reverse to PO interleaving, and temporarily stored inthe RAM 1402 b (Step 2004. Error correction is made for the data storedin the RAM 1402 b (Step 2005. The error corrected data is read from theRAM 1402 b (Step 2006, and by the EDC code 1006, it is checked whetherwrong correction is made or not. The checked data, from which additionalinformation such as ID or the like and a seed have been deleted, isoutput from the interface 311 (Step 2007.

In the case of conducting error correction processing after scramblingis released, random 1 byte error becomes 2 byte error due to errorpropagation of guided scrambler so that the number of errors isincreased. Accordingly, the number of errors to be corrected isdecreased under the same error correcting capability of the errorcorrecting code. Further, since the guided scrambler causes errorpropagation, it being taken into account that when error correction isdisabled, data is saved even in a small amount, it is desirable that asshown in the present embodiment, scrambling is performed along thewritten byte list in the case of conducting scrambling processing at theoptical disk medium side. According to the present embodiment, when alarge burst error occurs to disable error correction, scrambling can bereleased only with one byte error propagation from the final bit of theburst error.

FIG. 25 is a block diagram showing a fourth embodiment of an opticaldisk apparatus to which the invention is applied.

In the present embodiment, data is written on the optical disk in thephysical format shown in FIG. 21. In the present embodiment, as a runlength limited code, EFM plus used in the DVD is used. EFMPlus is (d,k)=(2,10) code, the minimum mark and space length is 3 channel bit, andthe maximum mark and space length is 11 channel bit. In FIG. 21, a SYNCpattern indicated by “SY” is a bit string shown in FIG. 23. The bitstring in FIG. 23 is expressed by NRZI form. “1” means that the mark andthe space are reversed, and “0” means that they are kept intact. As theSYNC pattern is clearly distinguished from the data, the SYNC patterncontains mark or space for 14 channel bit which does not exist in thedata part. One kind of a SYNC pattern is written following onescrambling seed. 256 scramble seeds are, as shown in FIG. 22, classifiedin 26 ways, and the seed appearing in one position on each physicalformat is limited to one way. For example, the seed in the firstposition of the physical sector is seedGr0, that is, selected from ninefrom the seed 0 to the seed 8.

The procedure of recording data will now be described.

The ID adding circuit 1401 adds ID and additional information to datainput from the interface 311 to form a data sector. The data sector istemporarily stored in the RAM 1402 a. The data is read from the RAM 1402a, and the lateral 172-byte data sector is divided into 91 bytes and 81bytes. The divided data are respectively scrambled by one seed selectedfrom the seeds contained in the classification shown in FIG. 24. Thescrambled data is, as shown in FIG. 24, written back to the RAM 1402 a.

The error correcting encoding circuit 307 calculates error correctingcodes PO, PI for the data written back to the RAM 1402 a. The datasubjected to error correcting code calculation is written in the RAM1402 a according to the format of FIG. 24. After that, while data isread from the RAM 1402 a, PO interleaving is performed. The encodingcircuit 305 converts the data subjected to PO interleaving to a runlength limited code, and a SYNC pattern of a fixed pattern is, as shownin FIG. 21, inserted therein to form a physical sector. The thusprocessed data is recorded on the optical disk 301 through the laserdriver 1405 by the optical pickup 302.

At the time of reproducing, the optical pickup 302 reads the datarecorded on the medium. The read channel 304 performs binarization andsynchronous clock generation for the read data. The decoding circuit 306decodes the scrambled data from the run length limited code.

The descrambling circuit 2501 conducts descrambling processing for thedecoded data, and searches for a SYNC pattern of a fixed pattern. Whenthe SYNC pattern is found, the descrambling circuit 2501 checks thedescrambled seed data immediately before the SYNC pattern, and storesthe data read on the basis of grouping of the read seed data in the RAM1402 b according to the recording format shown in FIG. 21. The datastored in the RAM 1402 b is subjected to error correction anddescrambled. After that, by the EDC code 1006, it is checked whetherscrambling is correct or not, and after error correction is made, wrongcorrection is made or not. Additional information such as ID or the likeand the seed are deleted to output data to the interface 311.

The processing is thus conducted, whereby scrambling is performed inunits of 91 bytes of the user data, so that error propagation due toscrambling is kept from being propagated outside the 91 bytes.Furthermore, it is uniquely known to which position of the recordingsector the read data corresponds. Further, the additional bit requiredfor the SYNC pattern and the scrambling seed is 26 bits per one sectoras compared with the conventional DVD, addition of about 1.6 byte perone sector will be sufficient.

Further, according to the present embodiment, it is sufficient toprovide only a single SYNC pattern, and it is not necessary to provideplural SYNC patterns for knowing the position in the sector.Accordingly, design for the run length limited code can be veryfacilitated. In the optical disk, since low-frequency noise is much, ahigh-pass filter is used in reproduction. Consequently, distortion iseasily caused immediately after a long mark and space. As the fixed SYNCpattern is needed to be clearly separated from another recorded code,generally a long mark and space not appearing in the recorded code areused in many cases. Accordingly, it is desirable to place the scrambleseed in front of the fixed SYNC pattern.

A fifth embodiment will now be described with reference to FIGS. 26 and27. The fifth embodiment is different from the second embodiment in thatscrambling is performed before data is stored in RAM. As shown in FIG.26, a scrambler 1 (2601 and a scrambler 2 (2602, that is, two scramblingcircuits are provided, and the scrambler 1 is the scrambling circuitshown in the first embodiment. First, at the time of recording, the datainput from the interface 311, to which ID and additional information areadded in the ID adding circuit 1401, is scrambled by the scrambler 1(2601, and then temporarily stored in the RAM 1402 a. Subsequently, anerror correcting code is calculated in the error correcting encodingcircuit 307, and PO redundant byte and PI redundant byte are stored inthe RAM. PO interleaving is performed while reading from the RAM, andthe data is converted to a run length limited code in the encodingcircuit 305, which is recorded on the optical disk 301 by controllingthe optical pickup 302 through the laser driver 1405. When the data forone ECC block is normally recorded on the optical recording medium, itcomes to an end. In the case where a recording failure is caused in themidway by some reason, however, when the same data is written in thesame place, the medium is deteriorated, so the seed is changed toperform re-scrambling and try again. In that case, the data stored inthe RAM is scrambled by the scrambler 2 (2602 and again stored in theRAM, an error correcting code is again added by the error correctingencoding circuit, then PO interleaving is performed, a run lengthlimited encoding is performed, and re-writing is performed. Thescrambler 2 (2602 circuit is shown in FIG. 27. In this circuit, theswitch 2701 is turned down toward the first 8-bit seed, and thencontrolled toward “0”. From the seed direction, a suitable 8-bit seedbit string is input at every time. An exclusive OR of the M-sequencegenerated by this circuit and the scrambled data stored in the RAM isoperated bit by bit to perform re-scrambling with different seeds. Atthe time of reproducing, reproduction may be performed similarly to thesecond embodiment.

According to the invention, an arbitrary seed data is added to theoriginal data to be recorded on the disk to scramble the data, wherebyplural ways of scramble can be conducted depending on the selection ofseed data. Accordingly, even if a large amount of the same data iswritten on the adjacent track, the written data of the adjacent trackcan be prevented from being the same data. Further, even in the casewhere the same data is written in the physically same position, actuallythe written data are made different, so that the medium can be preventedfrom being deteriorated.

According to the invention, one-bit descramble data is determined byoperation using plural-bit scramble data, whereby it is not necessary toknow the seed data at the time of descrambling, so that descrambling canbe performed by the simple same procedure.

Further, according to the invention, one-bit descramble data isdetermined by operation using n-bit scramble data. When the n-bitscramble data has an s-bit length, the error of descramble data is justextended by s-bit to the error of the scramble data, whereby it ispossible to prevent the situation that the whole data can not bedescrambled.

Further, according to the invention, guided scramble and scramble with along-period fixed seed are used jointly, so that sufficient randomizingfor the data can be secured.

Further, according to the invention, scramble is conducted before thegeneration of an error correcting code, and descramble is conductedafter decoding of the error correcting code, whereby the decodingcharacteristic of the error correcting code can be prevented from beingdeteriorated by error propagation due to scramble.

1. A data-randomizing method for an optical disk apparatus adapted torecord data on recording medium by light, and read data from therecording medium by utilizing a difference in reflectance, comprising:adding seed data for randomizing, to subject data to be recorded on therecording medium, and determining at least one bit randomized data byoperating at least one bit data added seed data to the subject data andmultiple bit randomized data which was made from at least one bit dataadded seed data and multiple randomized bit data, wherein a differentvalue of seed data is used as the seed data for every time of rewritingdata, and wherein the seed data is data which is produced by using adifferent value for every time of rewriting data to a same addresslocation of the recording medium.
 2. A decoding method for randomizingdata used in an optical disk reading apparatus adapted to readrandomized data by the method according to claim 1, comprisingdetermining one-bit de-randomized data by an operation using multiplebit randomized data.
 3. An optical disk recording medium for recordingdata by light, and enabling reading data recorded thereon by utilizing adifference in reflectance, in which data is randomized and writtenthereon by: adding seed data for randomizing data, to subject data to berecorded on the optical disk recording medium; and determining at leastone-bit randomized data by operation using at least one-bit data to beadded by seed data to the subject data and multiple-bit randomized datawhich was made from at least one bit data added seed data and multiplerandomized bit data, wherein the seed data is data which is produced byusing a different value for every time of rewriting data, and whereinthe seed data is data which is produced by using a different value forevery time of rewriting data to a same address location of the recordingmedium.
 4. An optical disk apparatus using the data-randomizing methodaccording to claim 1, wherein data recorded on the recording medium isdata recorded by adding error corrected code after randomizing by thedata-randomizing method.
 5. An optical disk apparatus for reading datarecorded by using the method data-randomizing according to claim 1,wherein the subject data which is added by error correction code to beread from the recording medium is de-randomized data after errorcorrection.
 6. A data-randomizing method for an optical disk apparatusadapted to record data on recording medium by light, and read the dataon the recording medium by utilizing a difference in reflectance, addingrandomized data based on seed data to user data by performing anexclusive OR operation of a first data randomizing method to producefirst randomized data, which is randomized by a second data-randomizingmethod according to claim
 1. 7. A data-randomizing method according toclaim 1, wherein data is randomized in every fixed unit, and data of afixed unit contains address identification information including atleast ID, user data, and an error detection code.
 8. A data-randomizingmethod according to claim 1, wherein data is randomized in every fixedunit, and data of a fixed unit contains seed data, addressidentification information including at least ID, user data, and anerror detection code.
 9. A data-randomizing method according to claim 1,wherein data is randomized in every fixed unit for recording, and seeddata is placed in front of a synchronous signal.
 10. An optical diskapparatus according to claim 4, wherein an order of data arrangement fordata randomizing is similar to an order of an error correction code wordfor decoding.
 11. An optical disk apparatus using the data-randomizingmethod according to claim 1, wherein subject data recorded on therecording medium is recorded by adding an error correction code,data-randomization is performed after the error correction coding, andan order of data arrangement for data randomizing is similar to an orderof recording data on the recording medium.
 12. A data-randomizing methodfor an optical disk apparatus adapted to record data on recording mediumby light, and read data from the recording medium by utilizing adifference in reflectance, comprising: adding seed data for randomizing,to subject data to be recorded on the recording medium, and determiningat least one bit randomized data by operating at least one bit dataadded seed data to the subject data and multiple bit randomized data,wherein a different value of seed data is used as the seed data forevery time of rewriting data, and wherein the seed data is data which isproduced by using a different value for every time of rewriting data toa same address location of the recording medium.
 13. An optical diskrecording medium for recording data by light, and reading data recordedon the optical disk recording medium by utilizing a difference inreflectance, in which data is randomized and written thereon by: addingseed data for randomizing data, to subject data to be recorded on theoptical disk recording medium; and determining at least one-bitrandomized data by operation using at least one-bit data to be added byseed data to the subject data and multiple-bit randomized data, whereinthe seed data is data which is produced by using a different value forevery time of rewriting data, and wherein the seed data is data which isproduced by using a different value for every time of rewriting data toa same address location of the recording medium.